The present invention relates to an oxygen mask which is attached to the patient to supply oxygen thereto, and more particularly to an oxygen mask to and from which an expired gas concentration measurement sensor is attachable and detachable.
An oxygen diffuser which supplies oxygen to the patient is disclosed in JP-T-2004-507333. The oxygen diffuser disclosed in JP-T-2004-507333 is described as follows with reference to FIG. 8.
The diffuser 20 shown in section in FIG. 8 has a body 31 formed from a wall 32, of somewhat triangular, cup-shaped appearance which follows the shape of the nose/mouth nexus of a patient. This wall extends from a base 33 where an oxygen outlet 34 is positioned, outwardly and upwardly to an edge 35 of triangular peripheral shape. As it approaches this edge 35, wall 32 becomes more “vertical” (with opposite sides being parallel) than outwardly extending. This shaping of the body wall permits a concentration of the oxygen and a shaping of the plume of oxygen-enriched, thus providing a more precise direction of this plume towards the patient's nose/mouth contour. The peripheral corners are rounded, with one of the corners 36, intended to be the uppermost corner when in use, and the proximal portions of the wall edge, are raised with respect to the other corners and edge portions as illustrated, also to facilitate the direction of oxygen towards a patient's nose and mouth. This construction, with protruding corner 36 and proximal edges of the wall, being positioned proximal to the patient's nose when in use, and the wider triangular portion at the bottom proximal a patient's mouth, provides optimal oxygen delivery to a patient.
A mushroom-shaped baffle 40, having a central post 42 which is seated in and over the oxygen outlet 34, is provided to assist in the diffusion of oxygen and avoid a direct flow of oxygen towards the patient's face. The upper end of baffle 40 has a curled-back lip 42 of conical shape so that oxygen flowing from the oxygen outlet 34 is directed into and against the underside 44 of this lip, creating turbulence and mixing the pure oxygen with the ambient air.
In other words, baffle 40 impedes oxygen flow directly from base 33, changing the oxygen transmission flow from a jet to a turbulent, plume-like flow.
Centrally located with post 42, extending from its bottom and through upper end 44, is a passageway 48 to permit gas analysis of expired gases from the patient. The passageway 48 provides a fluid communication from the environment in front of the patient's mouth and nose (when the delivery system is in operation) to the oxygen/carbon dioxide inlet port 28.
As a further configuration for supplying oxygen to the patient, JP-A-2006-68471 discloses an art in which tubes are inserted into the nostrils of the patient to supply oxygen thereto.
As a further configuration for supplying oxygen to the patient, JP-A-2005-253925 discloses an art in which oxygen is supplied to the patient through a mask which covers the nostrils and mouth of the patient.
As shown in FIG. 8, the diffuser 20 disclosed in JP-T-2004-507333 is configured by the wall 32 of somewhat triangular, cup-shaped appearance which follows the shape of the nose/mouth nexus of the patient. Therefore, the supply of oxygen and the concentration measurement of the expired gas can be simultaneously performed. However, the diffuser causes oxygen to directly flow into the nose and the mouth, and hence there is a problem in that the expired gas is diluted by oxygen and the concentration of the expired gas cannot be correctly measured. Particularly, it is very difficult to perform the measurement on mouth respiration.
Particularly, the expired gas concentration measurement used in JP-T-2004-507333 is performed by the side stream system in which the expired gas must be sucked through a sampling tube such as a tube 24. Therefore, also supplied oxygen is sucked, and there is a possibility that the expired gas is diluted.
In the oxygen supply which is performed through the tube, and which is disclosed in JP-A-2006-68471, there is a problem in that oxygenation is not performed in the case of mouth respiration. When a large amount of oxygen is supplied in order to enhance the efficiency of oxygenation, the nostrils are dried. Therefore, oxygen of a predetermined amount or more cannot be supplied.
In the oxygen supply which is performed through the mask, and which is disclosed in JP-A-2005-253925, there is a problem in that the interior of the mask is airtight and hence high concentration CO2 which has been expired is again inspired. In order to prevent such rebreathing from occurring, oxygen must be supplied at a rate of 5 L per minute or more. Therefore, there are problems such as that oxygen is wastefully used, and that, during attachment of the mask, the eyes are dried.